Patent GB-780779-A (GB)
Title: Aircraft flight simulating apparatus
IPC: G09B9/14
Filed: 1955-07-06
Abstract: 780,779. Grounded aircraft trainers. LINK AVIATION, Inc. July 6, 1955 [July 6, 1954; Sept. 22, 1954], No. 19604/55. Class 4. A method of simulating flight in an aircraft comprises deriving one or more control potentials which are functions of flight parameters of the aircraft, and applying potentials which are transient functions of the control potentials, to servo mechanisms associated with a dummy cockpit to displace the same from a reference position so that a trainee experiences the appropriate sensations, and to return the same to the reference position substantially unnoticed by the trainee. The cockpit 35 is shown in Fig. 1, as being rotatably mounted about a rolling axis on shaft 31 to a gimbal frame 28, which is rotatably mounted as by shaft 26 to a gimbal frame 20 supported by arms 16,17, 18, 19 or a hub 15 rotatably mounted on a pylon 11, whereby the cockpit can be moved in roll, pitch, and yaw, by motors M-300, M-200, and M-100 respectively. The cockpit is splined to shaft 31, and is bodily moveable fore-and-aft by a hydraulic piston and cylinder CYL-T. Similarly, the frame 20 and the cockpit are movable laterally by a piston and cylinder CYL-Y and the hub 15 is movable vertically by a further piston and cylinder, Fig. 2 (not shown). A control potential Xa is derived from a conventional flight computer, and a potential Xs is derived from this according to the equation:- or, if p is the differential operator, In Fig. 3a, the potential Xa is fed to one input of a summing amplifier 1, which controls a cockpit positioning servo 2. A device 3 derives an analogue signal proportional to the displacement of the cockpit 35, which signal is integrated and fed as another input to amplifier 1. The potential applied to the servo 2 is the Xs as above defined. Other circuits are shown in Figs. 3b-3e (not shown) suitable for deriving Xs from #Xa or #Xs from #Xa, some involving rate feedback devices instead of a positional feed back device 3. Fig. 4 shows a system for actuating the cockpit in roll, based on Fig. 3a. An amplifier U-401 passes on an angle of bank signal from the conventional flight computer to the summing amplifier U-402 (equivalent to amplfiier (1), which feeds a servo amplifier U-403 and servomotor M-300 acting on shaft 31 to rotate the cockpit 35. A follow-up potentiometer R-401 derives a signal proportional to the angle of roll fed to an integrator U-404, the output of which forms a second input to amplifier U-402. If the controls are actuated to cause a sudden bank, the cockpit 35 will rotate on shaft 31. The output of integrator U-404 will then build up, slowly returning the cockpit to the neutral position. Potentiometer R-401 may be non linear, so that the cockpit is displaced according to the computed angle of bank for smaller angles, but rotates proportionately less for larger computed angles. The cockpit instruments indicate the computed angles. In Fig. 5, the cockpit 35 is adjustable in height and pitch by two hydraulic pistons and cylinders 501, 502 controlled by valves V-501 and V-502. The altitude servo of the flight computer positions the arm of a potentiometer R-501 to derive an impulse on change of simulated height which is passed by capacitor C-501 and resistors R-511 and R-512 to amplifiers U-501 and U-502 controlling the valves V-501 and V-502, to raise or lower the cockpit bodily, giving the trainee a sensation of rising or falling. Feed back signals are derived from potentiometers R-513 and R-514. The charge on capacitor C-501 leaks awaythr ough resistor R-515, so that the cockpit is gradually returned to its datum position unnoticed by the trainee. The potential Xs applied to amplifier U-501 is thus related to the potential Xa derived from potentiometer R-501 by an equation of the type quoted above. The pitch angle servo operates the arms of two potentiometers R-502 and R-503 to derive equal and opposite signals which are fed to capacitor resistor combinations, and which operate the pistons and cylinders 501 and 502 equally in opposite senses to pitch the cockpit when a change in computed pitch occurs, and slowly to return the cockpit to its datum position. Fig. 6 (not shown) discloses apparatus for operating piston and cylinder CYL-Y from the inner lateral acceleration servo, Figs. 7, 8 and 9 Figs. 8 and 9 (not shown) disclose systems in which the reference position of the cockpit can be altered in accordance with the computed parameters of flight. In Fig. 7, the trainee bank angle servo actuates the cockpit 35 in roll through elements C-701, R-706, R-707, amplifier U-702, servo M-300, and positional feed back device R-708, R-709 as in Fig. 4. When, however, the -computer indicates a net lateral force as acting on the aircraft simulated, the cockpit is rolled permanently, so that a component of gravity acts laterally on the trainee to simulate these lateral forces in a permanent manner, transient changes due to changes in bank angle being superimposed. The Y-axis force computer servo positions the wiper of a potentiometer R-701 deriving a signal fed to an amplifier U-701, so that if a turn is incorrectly banked, a signal is passed to the #y computer, where #y is the angle in the lateral plane between the Z-axis and the resultant force on the aircraft. The #y signal is passed through a delay filter 710, and fed to amplifier U-702 to determine a new datum position for the cockpit. The Z-axis force computer positions the arm of a potentiometer R-721 which alters the feed back impedance of amplifier U-201, so that the net Y force is effectively divided by the net Z-force, the #y computer then having a transfer function of arc tangent. Since the cockpit arrangement of Fig. 1 is not capable of giving the trainee an impression of downward acceleration of more than g, the Z force computer also positions the arm of a potentiometer R-720 which is earthed at a point in its winding corresponding to a downward acceleration of g. When the wiper passes this point, it derives a potential which passes a rectifier X-702 and operates a relay K-701, which disables the #y computer, and returns the cockpit datum position to the reference position. Fig. 9 (not shown) discloses an analogous pitch system, and Fig. 8 (not shown) a roll system in which the datum position of the cockpit is controlled by a ball angle computer used for controlling the ball of a lateral force indicator.